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The new Upflow Algae Scrubber (UAS)

This new test version of the algae scrubber is much easier to build than the waterfall version. This new scrubber has never been posted before May 2012. It works in both freshwater and saltwater.

If you are like most aquatic hobbyists, nuisance algae is an ongoing problem. You try to feed your livestock, and the next thing you know, you get algae. You've already tried many fixes; some work but are expensive; some kind of work but you're not sure; and some just don't work at all.

Think about what is happening: Your aquarium is accumulating nutrients (nitrate and phosphate) because of the food you feed. Algae eat nitrate and phosphate to grow, so the algae are having a great time growing in your water because they are eating all your nutrients! What to do?

Well think about this: In order to grow, algae must be provided with nitrate and phosphate. So why can't you just use the algae to consume all the nitrate and phosphate? The answer: You can! How? With a simple device you build called an Upflow Algae Scrubber. It's simple, cheap, and you can make a small one in just a few minutes with parts you probably already have. Here are some pics of the most basic test design; it probably won't be your final version, but it will get you started:

An "algae scrubber" is a simple filter that actually grows algae in the filter, so that the algae do not grow in other parts of your aquarium. Simply put, the conditions for algae growth inside the filter are better than the conditions in the rest of your aquarium; thus the algae grow in the filter instead of your aquarium, and then you just remove the algae from the filter and throw the algae away. But in order for the algae to grow in the filter, the algae need to consume nitrate and phosphate; so guess where the nitrate and phosphate come from? Your water!

If you stop and think about it, algae always grow in certain spots, and not in others. This is because some of the three growing conditions (light, flow, nutrients) are better in some parts of your water than they are in others. An "upflow algae scrubber" simply optimizes these conditions, and does so at a place where the algae can be easily removed and thrown away. And once the nitrate and phosphate have been removed from your water, all other nuisance algae such as green hair, bubble, turf and slime, will have a hard time staying alive.

So where have these filters been all this time, and why haven't you heard of them if they work so well? Well the original waterfall version (posted in August 2008) was hard to build, and was not really for sale anywhere; so unless you liked to build things from scratch, you had no choice but to buy some other kind of filter. All the filter really needed to do was to create good growing conditions (light, flow, nutrients) for the algae, by flowing the water across a piece of rough material, so that the algae would grow on the material instead of somewhere else in the aquarium. The waterfall algae scrubber did grow lots of algae in the filter, and it removed lots of algae from aquariums: Over 1,000 people built their own waterfall algae scrubbers, and reported their results on various forums during a 4 year period; almost all of them wiped out their nuisance algae within 8 weeks, and many did so in 4 weeks. And on other forums that I never posted on, an estimated 10,000 people built their own waterfall algae scrubbers with similar results.

A little over a year ago in April 2011, another idea came along: Instead of letting the water flow down a screen like a waterfall, how about you let the water flow up the screen using air bubbles? Why? Because as good as waterfall algae scrubbers are, they still need a place for the water to drain "down" to. This means that you need to have a sump below the aquarium, or you need to have the scrubber up above the aquarium. This is not easy, and is very difficult for a nano aquarium which usually has no sump below it, and no room above it. Also, the waterfall version requires it to be out of the water (in the air), which takes up extra space. The new "upflow" version, however, can be placed inside the aquarium, so that it takes up no extra space at all, and it needs no external plumbing or water pumps at all. Only air bubbles.

The Upflow Algae Scrubber (tm) (UAS) provides the best growing conditions for algae in your tank: Air bubbles provide rapid turbulent flow; Strong lighting provides the light; and the nutrients that are already in your water provide the nitrate and phosphate. All that's needed is a place for the algae to attach to, and that is provided by the roughed-up plastic screen. Thus the algae start growing on the screen because the flow and lighting are stronger there than they are in the rest of your aquarium; nitrate and phosphate are consumed in the process. This causes algae to start disappearing from your aquarium and start re-appearing on the scrubber screen, so that you can throw the algae away every week or two.

The most basic way to set up an Upflow Algae Scrubber, especially in small aquariums, is just to put some air bubbles beneath a vertical screen. If inside an aquarium, you just put a light on the outside of the glass, so that it shines inside to the screen. And if you want better performance (which means better filtering), just add a reflector to give the screen some light on both sides. The screen is best made with 7-mesh cross stitch plastic canvas that you get at sewing or craft stores, or online. Also, don't forget to rough up the screen with a sharp object like a hole saw; the screen should be so rough that the screen holes are almost filled in with all the little pieces of plastic that you roughed up.

One thing to remember is that an Upflow Algae Scrubber (or any algae scrubber) will not cause more algae to grow in your aquarium. Instead, the algae will disappear from your aquarium, and will start to grow on the scrubber screen instead. You then just remove the screen and scrape the algae off. And here's a surprise: Watch out for your fish or snails eating your filter! There's nothing tastier than live green algae, so your fish or snails may keep your screen from getting very thick. The simple solution is to just put some mesh or extra plastic canvas around it.

There are a couple of requirements that have been learned since August 2008 which will get you started quicker. The size of the Upflow Algae Scrubber that is needed is based on how much you feed, and not how much water you have, because the nutrients that cause algae to grow come from the food you feed. The following updated picture has size guidelines:

And the following updated picture has examples:

Thanks to floyd, russo, worley, spidey, rumpy, morgan, marksfish, doompie, kerry, jnad, and tebo for doing early testing. When posting your build pics, start a separate thread in this section, and title it "Username UAS Test".

Dude this can totally be done with an enclosed box. I can take the boxes I am making for type-I (which are built well enough to remain constantly full) or the SM100 even and plug the hole in the bottom, pump water into one side and let it drain out the other. Also since mine have a emergency drain bulkhead about 1/2 way up one side (that fits a uniseal or a 1" ABS BRS bulkhead) all I would need is an upturned elbow for a surface drain. This is totally do-able and so frickin stupid simple why didn't I think of this man!! Lucky for me I can easily convert all my designs over for literally nothing.

This is a super interesting concept. My only worry is scaling this up for larger tanks. For nanos this seems like an ace in the hole. I haven't really seen air stones large enough for bigger tanks. I guess the biggest I have seen them is around what 4" long?

I also see that we are going to be limited to one sided lighting for nanos if this goes in tank, so a painted black backing on a cube will make this hard to implement unless it is externalized. My guess is that lighting from the main tank will help algae grow.

Originally Posted by Floyd R Turbo

Dude this can totally be done with an enclosed box. I can take the boxes I am making for type-I (which are built well enough to remain constantly full) or the SM100 even and plug the hole in the bottom, pump water into one side and let it drain out the other. Also since mine have a emergency drain bulkhead about 1/2 way up one side (that fits a uniseal or a 1" ABS BRS bulkhead) all I would need is an upturned elbow for a surface drain. This is totally do-able and so frickin stupid simple why didn't I think of this man!! Lucky for me I can easily convert all my designs over for literally nothing.

This is my plan eventually with something like this. Seems like it is more efficient. You could totally get away with a standpipe-ish type drain and keep the hole in place and just keep the new modified box.